The present invention relates to an improved method for producing a wood-type golf club head, and more particularly relates to an improvement in production of a wood-type golf club head having a shell made of FRP (fiber reinforced plastics) or metal.
Japanese Patent Publication No. sho.51-21436 discloses one conventional example of such a wood-type golf club head. The golf club head includes a hollow FRP shell whose cavity is filled with foam resin. Such a structure, however, does not allow successful weight balance adjustment.
In the case of a solid golf club head made of wood, weight balance adjustment is well carried out by forming one or more holes in the body and filling corresponding number of mass pieces into the holes. Such a manner of weight balance adjustment is accompanied with no significant problems.
This, however, cannot be said for the above-described type of golf club head having a hollow shell. In this case, a threaded hole is formed in the shell and a mass piece is screwed directly into the threaded hole. This mechanism basically depends on the thread engagement for fixation of the mass piece for weight balance adjustment. This thread engagement, however, is quite unreliable due to the relatively small thickness of the shell and the fixation is poorly endurable against shocks at shooting balls. Thus, loose attachment of the mass piece tends to allow undesirable displacement of the mass piece, and in the worst case separation of the mass piece, thereby seriously disturbing balance of weight of the golf club head.